Viscoelastic study of the creep behavior of GeS2-SbS3/2-SnS and GaS3/2-SbS3/2-SnS glasses around their deformation temperatures

Abstract

A viscoelastic study of the 25GeS2-55SbS3/2-20SnS and 12.5GaS3/2-75SbS3/2–12.5SnS sulfide glasses was carried out around their deformation temperatures using a uniaxial compression creep test. Their viscosities showed similar temperature dependences, but slightly lower sensitivity was observed for the latter glass than for the former glass, which may be explained by the theory of free volume. The creep function, derived from the displacement of the height of the sample subjected to a creep test, was converted into relaxation moduli by performing a Laplace transformation and its inversion. The shear relaxation moduli G(t) revealed two distinct structural relaxation processes, specifically with short and long relaxation times. Both the major fast-relaxation process and minor slow-relaxation process obeyed the time–temperature superposition principle. The fast-relaxation activation energies for both glasses were estimated to be about 390 kJ/mol. This value was close to the dissociation energy of the Sb—S bond, which formed the major cross-links of the glass network. In contrast, slow-relaxation activation energies of approximately 590 and 550 kJ/mol were determined for the GeS2-containing and GaS3/2-containing glasses, respectively. The slow-relaxation process, having a higher activation energy for the GeS2-containing glass than for the GaS3/2-containing glass, was concluded to have involved dissociation and recombination, even at high temperatures, of the stronger crosslinks made of the Ge—S and Ga—S bonds in the glass network.